1. Field of the Invention
The invention relates to a network element of an analog, cellular network, notably a mobile radio set or a base station, as well as to a method for a network element of an analog, cellular network for receiving a wide-band data sequence that is composed of a starting synchronization, a word synchronization, a data word and a fixed number of repeats of a further synchronization, a word synchronization and the data word.
2. Discussion of the Prior Art
The transmission of data with the described format is intended, for example, for the US system AMPS (Advanced Mobile Phone System) that is known from the standards TIA/EIA/IS-91 (“Mobile Station—Land Station Compatibility Standard for 800 MHz Analog Cellular”, 1994) and TIA/EIA/IS-136.2-A (“TDMA Cellular/PCS—Radio Interface—Mobile Station—Base Station Compatibility—Traffic Channels and FSK Control Channel”, October 1996) for the message channel Forward Voice Channel (or FVC) from a base station to a mobile radio set. The data sequence to be used for this channel amounts to 1032 bits and is shown for a transmitted word, by way of example, in FIG. 1. A long starting synchronization “DOT1” of 101 bits is succeeded by a word synchronization “WS” with 11 bits and the first transmission of the data word “REP1” to be transmitted with 40 bits. Subsequently, there are 10 repeats of a shorter synchronization “DOT” with 37 bits, of a word synchronization “WS” with 11 bits, and of the data word “REP2-REP11” to be transmitted. The starting synchronization (DOT1) as well as the further synchronizations (DOT) therein consist of a “dotting” sequence consisting of alternating zeros and ones.
Wide-band data sequences of this kind are used for the transmission of a single data word, for example, for hand-over requests from a base station to a mobile radio set during an on-going analog speech transmission, in order to trigger the mobile radio set to change over to a channel with a better reception quality in the case of poor reception.
If more than one data word is to be transmitted, for example in the framework of short messages or for an exchange of authentification data, the data sequence of 1032 bits shown in FIG. 1 will be successively used for each of the data words to be transmitted.
In the case of an analog speech transmission, the part of a network element that serves to decode data sequences received must continuously monitor the audio stream during the speech transmission in order to detect any wide-band data transmissions. For normal implementations within the framework of AMPS the recognition of a 101-bit starting synchronization is used to assume that a data transmission has commenced. The network element should subsequently be synchronized in conformity with the 101-bit starting synchronization and the word synchronization before the various repeats of the actual data word can be received. Each of the repeats of the data word is customarily encoded with a 40,28 BCH (Bose-Chaudhuri-Hocquenghem) code, so that some errors in the data word can be recognized and even be corrected, if necessary. After having received the eleven repeats of the data word, the network element can perform a selection procedure on the stored repeats of the data word and apply the data word ultimately selected to a further processing item.
The implementations that are known from practice have the drawback that data words of a received data sequence are not detected when the starting synchronization has not been recognized because of poor receiving conditions, so that in that case the message is lost. Consequently, for example, necessary hand-overs cannot take place so that an on-going speech connection could be interrupted in a particularly bad case.